Genetic Control of Otic Induction Sensorineural hearing loss due to auditory hair cell damage affects millions of Americans. Embryonic stem cells are a potential source for generation of otic progenitors and hair cells that could be highly useful for cell replacement therapies, developmental studies, and other applications. In order for the stem cell system to reach its full potential to recapitulate otic development and generate pure sensory epithelia in vitro, two critical barriers must be addressed. The first barrier is a lak of biomarkers unique to the otic sensory lineage that would enable unambiguous identification of otic cells. The second barrier is poor understanding of the genetic regulation of otic gene expression and lack of tools for live reporting in cells and embryos for purification of otic cell types. The overall goal of this project is to address these barriers through combined study of mouse inner ear development and stem cell culture to further our understanding of the molecular genetics of otic specification. This will be achieved in aim 1 by characterizing the expression and cell-fate lineage of the gene Fbxo2, which we identified as a highly specific otic sensory marker gene that spans developmental stages. In aim 2, we will characterize mouse and human promoter/enhancer elements that regulate expression of this gene. Aim 3 will evaluate Fbxo2 expression in stem cell derived otic progenitors, test the hypothesis that this gene is activated synergistically by specific otic transcription factors, and utilize Fbxo2 promote-driven reporters to purify stem cell-derived otic progenitors and solve the issue of stem cell heterogeneity. Achieving the proposed aims will: 1) improve knowledge of the genetic control of otic induction, 2) produce tools that target inner ear progenitors and sensory cells, 3) enable the in vitro culture and propagation of highly pure otic progenitors and 4) generate knowledge and tools for gene targeting and transplantation therapies for the inner ear.